The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. However, these advances have increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed.
In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling-down also produces a relatively high power dissipation value, which may be addressed by using low power dissipation devices such as complementary metal-oxide-semiconductor (CMOS) devices.
During the scaling trend, various materials have been implemented for the gate electrode and gate dielectric for CMOS devices. CMOS devices have typically been formed with a gate oxide and polysilicon gate electrode. There has been a desire to replace the gate oxide and polysilicon gate electrode with a high-k gate dielectric and metal gate electrode to improve device performance as feature sizes continue to decrease.
As the technology continues to be scaled down, e.g., for 28 nanometer (nm) technology nodes and below, metal gate electrodes with narrow widths may introduce an issue of high gate resistance. The issue of high gate resistance may affect the electrical performance of CMOS devices. For example, the high gate resistance may degrade the maximum oscillation frequency (fmax), noise, and stability of radio frequency CMOS (RFCMOS) devices performing at high frequencies.